The present invention relates to a physical quantity distribution sensor, a method of driving said sensor and a method of producing said sensor.
Recently, there is increased a demand for a semi-conductor device for sensing the spatial distribution of a physical quantity in a variety of fields. Particular attention is placed on a solid-state imaging device for sensing a light quantity as the physical quantity. More specifically, such a so-called amplifier-type solid-state imaging device is designed in the following manner. A plurality of storage sections are arranged to store a signal electric charge obtained through photo-electric conversion at the associated one of a plurality of photoelectric conversion sections. Each storage section is connected to the operation control portion of a transistor such as the gate of a field-effect transistor (FET) or the base of a bipolar transistor, or provision is made such that the storage section also serves as an operation control section. Accordingly, an electric current flowing in each transistor is controlled based on that potential of the associated storage section which varies with the amount of a signal electric charge.
With reference to FIG. 12, the following description will discuss the arrangement and operation of a physical quantity distribution sensor of prior art with an amplifier-type solid-state imaging device taken as an example.
As shown in FIG. 12, pixels 2 are arranged in a plurality of rows and a plurality of columns in an imaging region (generally, a region in which a physical quantity is to be sensed and stored) 1. Each pixel 2 comprises a photoelectric conversion/storage section 3 and a driving transistor 5 having a gate 4.
A selected-row-driving transistor 10 is disposed in each selected-row-driver 8, and a voltage is to be supplied to each selected-row-driving transistor 10 from a selected-row-driving-voltage input portion 9. Whether or not each selected-row-driving transistor 10 is electrically conductive, is controlled by a voltage of each output portion 7 of a shift register for row selection 6. An output of a selected-row-driving transistor 10 is connected to a plurality of row-select-transistors 12 arranged in the row through one of row selection lines 11, which allows a single pixel row to be selected out of the plurality of pixel rows.
The row-select-transistors 12 arranged in the same column are connected to a corresponding one of load transistors 14 through one of vertical signal lines 13. The output potential of each photoelectric conversion/storage section 3 varies with the amount of signal electric charge stored therein. The output potential of each photoelectric conversion/storage section 3 is given to the gate 4 of a corresponding driving transistor 5 which is connected to one of power supply lines 17. There is formed a source follower circuit in which the driving transistor 5 serves as a driving transistor and in which the load transistor 14 connected to a second power supply voltage (Vss) terminal 15 and to a gate input portion 16, serves-as a load transistor. A power supply voltage.(Vdd) is supplied to each power supply line 17 from a first power supply voltage (Vdd) terminal 27.
An output of the source follower circuit including the driving transistor 5 and the load transistor 14 is supplied to one of horizontal signal lines 24 through a signal column selection transistor 23 disposed in the associated one of column selection drivers 22. Whether or not signal column selection transistors 23 are electrically conductive, is controlled by voltages generated at output portions 21 of a shift register 20 for column selection. According to this control, a single pixel column is selected out of the plurality of pixel columns. An output of the source follower circuit in a selected column, is selectively sent to an impedance conversion section 25 through the horizontal signal line 24, and then supplied to an output portion 26 through the impedance conversion section 25.
After the signals are read out from all the pixels 2 arranged in the selected row, a reset voltage input portion 28 sends a reset voltage to the selected-row-reset-driving transistor 29 in the selected-row-driver 8 for the selected row, thereby to drive the pixel reset transistors 30 in the selected row through a pixel-reset-voltage-supply line 19 associated with the selected row. This resets the signal electric charges stored in the photoelectric conversion/storage sections 3 in the selected row. Then, these photoelectric conversion/storage sections 3 again start storing signal electric charges.
According to the above-mentioned arrangement of prior art, each pixel has a photoelectric conversion section and an electric charge storage section, or a photoelectric conversion/storage section 3 having both conversion and storage functions as in the above example, a row-select-transistor 12, a driving transistor 5 for amplifying an output of the photoelectric conversion/storage section 3, and a reset transistor 30 for resetting the electric charge stored in the electric charge storage section or the photoelectric conversion/storage section 3. Further, there are required a number of input/output lines such as the power supply lines 17 for driving transistors, the row-select-lines 11, the pixel-reset-voltage-supply lines 19, the vertical signal lines 13 and the like.
This complicates each pixel in arrangement and makes it difficult to enhance the performance thereof. It is also difficult to reduce each pixel in area to increase the number of pixels in the same area and to reduce the device in size.
In view of the foregoing, it is an object of the present invention to provide a physical quantity distribution sensor reduced in the number of input lines connected to pixels to simplify the pixels in arrangement, thus enabling to increase the number of pixels in the same area and to reduce the device in size.
The present invention provides a physical quantity distribution sensor comprising: a plurality of sensor/storage sections each having a sensor element for sensing a received physical quantity and a storage element for storing the information of physical quantity sensed by the sensor element; a selector for selecting at least one of the plurality of sensor/storage sections; and a plurality of buffers each capable of detecting and supplying the information stored in at least one selected sensor/storage section, and wherein there is disposed at least one selection signal transfer line for transferring an output of the selector, that power supply input portions of the buffers are connected to the selection signal transfer line, and that the buffers are operated using, as a power voltage, an output of the selector entered into the buffers through the selection signal transfer line.
The present invention provides another physical quantity distribution sensor having a plurality of unit cells arranged in N rows and M columns (each of N and M being a natural number not less than 2), each of the plurality of unit cells comprising (i) a sensor/storage section having (a) a sensor element for sensing a physical quantity and (b) a storage element for storing the information of physical quantity sensed by the sensor element, and (ii) a reset element for resetting the storage element, and this physical quantity distribution sensor is characterized in that there are disposed: a row selector for selecting one row out of the N rows; buffers in the M columns each for detecting and supplying the information stored in the storage element of the sensor/storage section in a selected row; and N selection signal transfer lines each for transferring an output signal of the row selector to each of the N rows, and that power supply input portions of the buffers in the M columns are connected to the N selection signal transfer lines and arranged to receive a power voltage through the selection signal transfer line in a selected row.
The present invention provides a further physical quantity distribution sensor comprising: sensor/storage sections each of which is disposed in each of a plurality of unit cells in a region to be sensed and stored and each of which comprises a sensor element for sensing a received physical quantity and a storage element for storing the information of sensed physical quantity; a plurality of buffers each of which is assigned to at least one sensor/storage section and each of which is arranged to detect and supply the information stored in the sensor element of the sensor/storage section; and a selector for selecting at least one sensor/storage section, and this physical quantity distribution sensor is characterized in that each of the plurality of buffers comprises an electric current control element for controlling the electric current flowing in each buffer, that an control input portion of each of the electric current control elements is connected to each of output portions of the selector, and that only the buffer assigned to the sensor/storage section selected by the selector is operated.
The present invention provides still another physical quantity distribution sensor having a plurality of unit cells arranged in N rows and M columns (N being a natural number not less than 1 and M being a natural number not less than 2), each of the plurality of unit cells comprising (i) a sensor/storage section having (a) a sensor element for sensing a physical quantity and (b) a storage element for storing the information of physical quantity sensed by the sensor element, and (ii) a reset element for resetting the storage element, and this physical quantity distribution sensor is characterized in that there are disposed: a column selector for selecting one column out of the M columns; and buffers in the M columns each for detecting and supplying the information stored in the storage element of at least one sensor/storage section in a selected column, and that output portions of the column selector are respectively connected to input portions of electric current control elements of the buffers.
The present invention provides a still further physical quantity distribution sensor having a plurality of unit cells arranged in N rows and M columns (N being a natural number not less than 1 and M being a natural number not less than 2), each of the plurality of unit cells comprising (i) a sensor/storage section having (a) a sensor element for sensing a physical quantity and (b) a storage element for storing the information of physical quantity sensed by the sensor element, and (ii) a reset element for resetting the storage element, and this physical quantity distribution sensor is characterized by comprising: a column selector for selecting one column out of the M columns; buffers in the M columns each for detecting and supplying the information stored in the storage element of at least one sensor/storage section in a selected column; a sensor output portion for externally supplying a signal supplied from the output portion of each of the buffers; an output signal transfer line connected to the sensor output portion directly or through an impedance conversion section; and switching elements arranged such that an electric current flows in the buffer in a column selected by the column selector.
The present invention provides a method of driving a physical quantity distribution sensor which comprises (i) sensor/storage sections each of which is disposed in each of a plurality of unit cells and each of which includes a sensor element for sensing a received physical quantity and a storage element for storing the information of physical quantity sensed by the sensor element, and (ii) buffers each for detecting and supplying the information stored in the storage element of at least one sensor/storage section, and in which at least one selection signal transfer line of a selector for selecting a portion of the plurality of unit cells, is electrically connected to power supply input portions of the buffers, and this driving method is characterized in that selection of a row to be read out is conducted by supplying a power voltage to the buffers of the row to be selected.
The present invention provides another method of driving a physical quantity distribution sensor which comprises (i) sensor/storage sections each of which is disposed in each of a plurality of unit cells and each of which includes a sensor element for sensing a received physical quantity and a storage element for storing the information of physical quantity sensed by the sensor element, and (ii) buffers each for detecting and supplying the information stored in the storage element of at least one sensor/storage section, and in which at least one selection signal transfer line of a first selector for selecting a portion of the plurality of unit cells, is electrically connected to power supply input portions of the buffers, and this driving method is characterized in that selection in the nth row to be read out is conducted simultaneously with selection of the (nxe2x88x921)th row to be reset.
The present invention provides a further method of driving a physical quantity distribution sensor which comprises (i) sensor/storage sections each of which is disposed in each of a plurality of unit cells and each of which includes a sensor element for sensing a received physical quantity and a storage element for storing the information of physical quantity sensed by the sensor element, and (ii) buffers each for detecting and supplying the information stored in the storage element of at least one sensor/storage section, and in which output portions of a second selector for column selection are connected to input portions of electric current control means of the buffers, and this driving method is characterized in that column selection and control of an electric current flowing in the buffer in a selected column are conducted at the same timing.
The present invention provides still another method of driving a physical quantity distribution sensor which comprises (i) sensor/storage sections each of which is disposed in each of a plurality of unit cells and each of which includes a sensor element for sensing a received physical quantity and a storage element for storing the information of physical quantity sensed by the sensor element, and (ii) buffers each for sensing and supplying the information stored in the storage element of at least one sensor/storage section, and in which a first input portion of an electric current control means of the buffer in the mth column is connected to a column selector at its output portion for the (mxe2x88x92a)th column (axe2x89xa71), and in which a second input portion of the electric current control means of the buffer in the mth column is connected to the column selector at its output portion for the (mxe2x88x92b)th column (bxe2x89xa71), and this driving method is characterized in that an electric current in the buffer in the mth column rises at the time when the (mxe2x88x92a)th column is selected, and falls at the time when the (mxe2x88x92b)th column is selected.
The present invention provides a method of producing a physical quantity distribution sensor having a plurality of unit cells arranged in N rows and M columns (each of N and M being a natural number not less than 2), each of the plurality of unit cells comprising (i) a sensor/storage section having (a) a sensor element for sensing a physical quantity and (b) a storage element for storing the information of physical quantity sensed by the sensor element, and (ii) a reset element for resetting the storage element, the physical quantity distribution sensor comprising: a row selector for selecting one row out of the N rows; buffers in the M columns each for detecting and supplying the information stored in the storage element of the sensor/storage section in a selected row; and N selection signal transfer lines each for transferring an output signal of the row selector to each of the N rows, power supply input portions of the buffers in the M columns being connected to the N selection signal transfer lines and arranged to receive a power voltage through the selection signal transfer line in a selected row, each of the buffers in the M columns having a source follower circuit comprising a plurality of driving elements assigned to the unit cells of each column and at least one load element connected to the driving elements, and this producing method is characterized by comprising: a step of forming the selection signal transfer lines; and a step of forming a wiring for connecting the driving elements to the load elements, these two steps forming two wirings different in level from each other.